Apache模块开发/用C语言扩展apache(1：简述)
linux_prog
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linux_prog 发表于 2007-06-19 17:32
Apache模块开发/用C语言扩展apache(1：简述)
from:http://www.loveopensource.com/?p=16
Apache模块开发/用C语言扩展apache(1：简述) by linux_prog Apache是一个非常稳定而且非常open的web server，它的很多功能都可以通过plugin的方式去扩展。 比如：mod_proxy使得apache可以作代理, mod_rewrite使得apache可以实现非常强大的url mapping和rewritting 功能，你是否也想自己来开发一个apache module呢？网上这方面的文章非常的少，而且全是E文， 希望我的这篇文章能够给你一些实质性的帮助。 开发apache module之前，我们有必要先分析一下其源代码。 $ cd httpd-2.2.4/ $ ls 其中：server/目录是apache核心程序的代码 include/目录存放主要的头文件 srclib/目录存放apr和apr-util代码(这两个是什么，后面介绍) modules/目录下存放目前已经有的各种module(可以看看这些代码先) $ cd include/ 先分析一下apache的头文件 $ vi httpd.h 第766行，这个结构非常的重要，后面编写模块时都要用到这个结构，所以分析一下。 每个http request都会对应这个结构的一个实例。 由于apache的源代码都有很详细的英文注释，所以我也不翻译了。 struct request_rec { /** The pool associated with the request */ //内存管理池，后面讲apr时会讲到 apr_pool_t *pool; /** The connection to the client */ conn_rec *connection; /** The virtual host for this request */ server_rec *server; /** Pointer to the redirected request if this is an external redirect */ request_rec *next; /** Pointer to the previous request if this is an internal redirect */ request_rec *prev; /** Pointer to the main request if this is a sub-request * (see http_request.h) */ request_rec *main; /* Info about the request itself… we begin with stuff that only * protocol.c should ever touch… */ /** First line of request */ char *the_request; /** HTTP/0.9, “simple” request (e.g. GET /foo\n w/no headers) */ int assbackwards; /** A proxy request (calculated during post_read_request/translate_name) * possible values PROXYREQ_NONE, PROXYREQ_PROXY, PROXYREQ_REVERSE, * PROXYREQ_RESPONSE */ int proxyreq; /** HEAD request, as opposed to GET */ int header_only; /** Protocol string, as given to us, or HTTP/0.9 */ char *protocol; /** Protocol version number of protocol; 1.1 = 1001 */ int proto_num; /** Host, as set by full URI or Host: */ const char *hostname; /** Time when the request started */ apr_time_t request_time; /** Status line, if set by script */ const char *status_line; /** Status line */ int status; /* Request method, two ways; also, protocol, etc.. Outside of protocol.c, * look, but don’t touch. */ /** Request method (eg. GET, HEAD, POST, etc.) */ const char *method; /** M_GET, M_POST, etc. */ int method_number; /** * ‘allowed’ is a bitvector of the allowed methods. * * A handler must ensure that the request method is one that * it is capable of handling. Generally modules should DECLINE * any request methods they do not handle. Prior to aborting the * handler like this the handler should set r->allowed to the list * of methods that it is willing to handle. This bitvector is used * to construct the “Allow:” header required for OPTIONS requests, * and HTTP_METHOD_NOT_ALLOWED and HTTP_NOT_IMPLEMENTED status codes. * * Since the default_handler deals with OPTIONS, all modules can * usually decline to deal with OPTIONS. TRACE is always allowed, * modules don’t need to set it explicitly. * * Since the default_handler will always handle a GET, a * module which does *not* implement GET should probably return * HTTP_METHOD_NOT_ALLOWED. Unfortunately this means that a Script GET * handler can’t be installed by mod_actions. */ apr_int64_t allowed; /** Array of extension methods */ apr_array_header_t *allowed_xmethods; /** List of allowed methods */ ap_method_list_t *allowed_methods; /** byte count in stream is for body */ apr_off_t sent_bodyct; /** body byte count, for easy access */ apr_off_t bytes_sent; /** Last modified time of the requested resource */ apr_time_t mtime; /* HTTP/1.1 connection-level features */ /** sending chunked transfer-coding */ int chunked; /** The Range: header */ const char *range; /** The “real” content length */ apr_off_t clength; /** Remaining bytes left to read from the request body */ apr_off_t remaining; /** Number of bytes that have been read from the request body */ apr_off_t read_length; /** Method for reading the request body * (eg. REQUEST_CHUNKED_ERROR, REQUEST_NO_BODY, * REQUEST_CHUNKED_DECHUNK, etc…) */ int read_body; /** reading chunked transfer-coding */ int read_chunked; /** is client waiting for a 100 response? */ unsigned expecting_100; /* MIME header environments, in and out. Also, an array containing * environment variables to be passed to subprocesses, so people can * write modules to add to that environment. * * The difference between headers_out and err_headers_out is that the * latter are printed even on error, and persist across internal redirects * (so the headers printed for ErrorDocument handlers will have them). * * The ‘notes’ apr_table_t is for notes from one module to another, with no * other set purpose in mind… */ /** MIME header environment from the request */ apr_table_t *headers_in; /** MIME header environment for the response */ apr_table_t *headers_out; /** MIME header environment for the response, printed even on errors and * persist across internal redirects */ apr_table_t *err_headers_out; /** Array of environment variables to be used for sub processes */ apr_table_t *subprocess_env; /** Notes from one module to another */ apr_table_t *notes; /* content_type, handler, content_encoding, and all content_languages * MUST be lowercased strings. They may be pointers to static strings; * they should not be modified in place. */ /** The content-type for the current request */ const char *content_type; /* Break these out — we dispatch on ‘em */ /** The handler string that we use to call a handler function */ const char *handler; /* What we *really* dispatch on */ /** How to encode the data */ const char *content_encoding; /** Array of strings representing the content languages */ apr_array_header_t *content_languages; /** variant list validator (if negotiated) */ char *vlist_validator; /** If an authentication check was made, this gets set to the user name. */ char *user; /** If an authentication check was made, this gets set to the auth type. */ char *ap_auth_type; /** This response can not be cached */ int no_cache; /** There is no local copy of this response */ int no_local_copy; /* What object is being requested (either directly, or via include * or content-negotiation mapping). */ /** The URI without any parsing performed */ char *unparsed_uri; /** The path portion of the URI */ char *uri; /** The filename on disk corresponding to this response */ char *filename; /* XXX: What does this mean? Please define “canonicalize” -aaron */ /** The true filename, we canonicalize r->filename if these don’t match */ char *canonical_filename; /** The PATH_INFO extracted from this request */ char *path_info; /** The QUERY_ARGS extracted from this request */ char *args; /** finfo.protection (st_mode) set to zero if no such file */ apr_finfo_t finfo; /** A struct containing the components of URI */ apr_uri_t parsed_uri; /** * Flag for the handler to accept or reject path_info on * the current request. All modules should respect the * AP_REQ_ACCEPT_PATH_INFO and AP_REQ_REJECT_PATH_INFO * values, while AP_REQ_DEFAULT_PATH_INFO indicates they * may follow existing conventions. This is set to the * user’s preference upon HOOK_VERY_FIRST of the fixups. */ int used_path_info; /* Various other config info which may change with .htaccess files * These are config vectors, with one void* pointer for each module * (the thing pointed to being the module’s business). */ /** Options set in config files, etc. */ struct ap_conf_vector_t *per_dir_config; /** Notes on *this* request */ struct ap_conf_vector_t *request_config; /** * A linked list of the .htaccess configuration directives * accessed by this request. * N.B. always add to the head of the list, _never_ to the end. * that way, a sub request’s list can (temporarily) point to a parent’s list */ const struct htaccess_result *htaccess; /** A list of output filters to be used for this request */ struct ap_filter_t *output_filters; /** A list of input filters to be used for this request */ struct ap_filter_t *input_filters; /** A list of protocol level output filters to be used for this * request */ struct ap_filter_t *proto_output_filters; /** A list of protocol level input filters to be used for this * request */ struct ap_filter_t *proto_input_filters; /** A flag to determine if the eos bucket has been sent yet */ int eos_sent; /* Things placed at the end of the record to avoid breaking binary * compatibility. It would be nice to remember to reorder the entire * record to improve 64bit alignment the next time we need to break * binary compatibility for some other reason. */ }; 可以看到源码中有很多apr_开头的结构，这个是什么呢？下节介绍一下。 |